This invention is concerned with reference electrodes having ceramic housings suitable for use in a high-pressure, high-temperature environment.
Reference electrodes having a ceramic housing, such as stabilized zirconia, are disclosed in U.S. Pat. Nos. 4,500,413, and 4,576,677, incorporated herein by reference. Such electrodes are suitable for use in high-pressure, high-temperature environments. Improved stability in the reference potential is provided by an annular liquid junction between the electrolyte within the electrode, and the liquid the electrode is immersed in. In the '413 and '677 patents a closely fitting ceramic plug is sintered in a hole in the ceramic housing of the electrode to form a porous bond therebetween. The porous bond forms the annular junction that provides for diffusion of ionic species into or out of the electrode, and for escape of the electrolyte when volume increases due to thermal expansion from rapid heating. The liquid junction also provides limited fluid transfer from the electrolyte to maintain chemical equilibrium and a stable concentration of ions in the electrolyte.
It is an object of this invention to provide a reference electrode suitable for use in high-temperature, high-pressure environments, having an annular liquid junction formed from a friction fitting.